Compounds barium

The first report concerning barium compounds occurred in the early part of the seventeenth century when it was noted that the ignition of heavy spar gave a peculiar green light. A century later, Scheele reported that a precipitate formed when sulfuric acid was added to a solution of barium salts. The presence of natural barium carbonate, witherite [14941-39-0] BaCO, was noted in Scodand by Withering. 

In its natural form, barium [7440-39-3] Ba, never occurs as the metal but is almost always found as the ore barite [13462-86-7] BaSO. More than 90% of all barium is actually used as the ore, albeit after preliminary beneftciation. The petroleum industry consumed 90% of the ore for oil- and gas-weU drilling duids (muds). The other 10% is used as filler and/or for extender uses and the manufacture of all other barium chemicals. Witherite, the only other significant natural barium ore, is not mined commercially (1). The quantity of U.S. barium chemicals produced in 1986 and 1987 is given in Table 1. 

Year Production, t Quantity, t Sold or used by processors Value, X 10  

Barium is a member of the aLkaline-earth group of elements in Group 2 (IIA) of the period table. Calcium [7440-70-2], Ca, strontium [7440-24-6], Sr, and barium form a closely aUied series in which the chemical and physical properties of the elements and thek compounds vary systematically with increa sing size, the ionic and electropositive nature being greatest for barium (see Calcium AND CALCIUM ALLOYS Calcium compounds Strontium and STRONTIUM compounds). As size increases, hydration tendencies of the crystalline salts increase solubiUties of sulfates, nitrates, chlorides, etc, decrease (except duorides) solubiUties of haUdes in ethanol decrease thermal stabiUties of carbonates, nitrates, and peroxides increase and the rates of reaction of the metals with hydrogen increase. 

In metallic form, barium is very reactive, reacting readily with water to release hydrogen. In aqueous solution it is present as an ion with a +2 charge. Barium acetate, chloride, hydroxide, and nitrate are water-soluble, whereas barium arsenate, chromate, duoride, oxalate, and sulfate are not. Most water-insoluble barium salts dissolve in dilute acids barium sulfate, however, requkes strong sulfuric acid. 

---

ALCOHOLS,HIGHERALIPHATIC - SURVEYAND NATURAL ALCOHOLSMANUFACTURE] (Vol 4) -in barium carbonate mgf [BARIUM COMPOUNDS] ( 7ol 3)... 

During this reaction, some barium ions remain in the solution as chlorides and can be uti1i2ed for the preparation of other barium compounds. 

One commercial process for producing sodium sulfide is as a by-product of barium carbonate production (see Barium compounds). Barite ore, BaSO, is reduced with carbon at 800°C to produce cmde barium sulfide (black ash), which is then leached to dissolve the barium sulfide in solution. The solution is then reduced using sodium carbonate to produce barium carbonate, leaving a weak sodium sulfide solution as the by-product. The sodium sulfide solution may then be concentrated and flaked or crystallized. 

Strontium has a valence of +2 and forms compounds that resemble the compounds of the other alkaline-earth metals (see Barium compounds Calcium compounds). Although many strontium compounds are known, there are only a few that have commercial importance and, of these, strontium carbonate [1633-05-2] SrCO, and strontium nitrate [10042-76-9], Sr(N03)2, are made in the largest quantities. The mineral celestite [7759-02-6], SrSO, is the raw material from which the carbonate or the nitrate is made. 

See Barium compounds Sulfur compounds Sulfuric and sulfurous esters. 

Most barium compounds are not as thermodynamically stable as the corresponding compounds of magnesium and calcium and therefore can be reduced by these metals. However, rather than producing pure barium, barium alloys are formed. Barium combines with most metals, forming a wide range of alloys and intermetaUic compounds. Among the phase systems that have been better characterized are those with Ag, Al, Bi, Hg, Pb, Sn, Zn, and the other Group 2 metals (12). 

Because of its high reactivity, production of barium by such processes as electrolysis of barium compound solution or high temperature carbon reduction is impossible. Electrolysis of an aqueous barium solution yields Ba(OH)2, whereas carbon reduction of an ore such as BaO produces barium carbide [50813-65-5] BaC2, which is analogous to calcium carbide (see Carbides). Attempts to produce barium by electrolysis of molten barium salts, usually BaCl25 met with only limited success (14), perhaps because of the solubiUty of Ba in BaCl2 (1 )-... 

Barium metal and most barium compounds are highly poisonous. A notable exception is barium sulfate which is nontoxic because of its extreme iasolubihty ia water. Barium ion acts as a muscle stimulant and can cause death through ventricular fibrillation of the heart. Therefore, care must be taken to avoid contact with open areas of the skin. Workers must wear respirators (of type approved for toxic airborne particles), goggles, gloves, and protective clothing at all times. The toxic barium aluminate residue obtained from barium production is detoxified by reaction with a solution of ferrous sulfate and converted iato nontoxic barium sulfate. According to OSHA standards, the TWA value for Ba and Ba compounds ia air is 0.5 mg/m. ... 

Most barium compounds are prepared from reactions of barium carbonate [513-77-9] BaCO, which is commercially manufactured by the "black ash" process from barite and coke ki a process identical to that for strontium carbonate production. Depending on the co-product, soda ash and/or carbon dioxide are also consumed. 

Side reactions of barium with siUcate impurities ki the ore have been noted (1,11—13). These reactions can cause appreciable loss of barium values by forming water-kisoluble barium compounds (14). For example, barium sulfate can form the orthosiUcate... 

Because of its extreme insolubiUty, barium sulfate is not toxic the usual antidote for poisonous barium compounds is to convert them to barium sulfate by administering sodium or magnesium sulfate. In medicine, barium sulfate is widely used as an x-ray contrast medium (see Imaging TECHNOLOGY X-RAY technology). It is also used in photographic papers, filler for plastics, and in concrete as a radiation shield. Commercially, barium sulfate is sold both as natural barite ore and as a precipitated product. Blanc fixe is also used in making white sidewall mbber tires or in other mbber appHcations. 

Toxicity. The toxicity of barium compounds depends on solubility (47—49). The free ion is readily absorbed from the lung and gastrointestinal tract. The mammalian intestinal mucosa is highly permeable to Ba " ions and is involved in the rapid flow of soluble barium salts into the blood. Barium is also deposited in the muscles where it remains for the first 30 h and then is slowly removed from the site (50). Very Httle is retained by the fiver, kidneys, or spleen and practically none by the brain, heart, and hair. 

Table 5. Acute Lethal Doses of Soluble Barium Compounds ...

Barium can also be deterruined by x-ray fluorescence (XRF) spectroscopy, atomic absorption spectroscopy, and flame emission spectroscopy. Prior separation is not necessary. XRF can be appHed directly to samples of ore or products to yield analysis for barium and contaminants. AH crystalline barium compounds can be analy2ed by x-ray diffraction. 

---